1. Field of the Invention
The present invention relates to a pallet stocker apparatus and more particularly to an art effectively applicable to the art of pattern printing including printing photoengraving patterns, printed circuit board patterns and plate patterns.
2. BACKGROUND OF THE INVENTION
In a conventional pallet stocker apparatus for a printer, a combination of printing pattern films such as mask, character and sandwich plates prepared according to the layouts of images of finished prints is inverted and exposed against an unexposed film to compose a positive.
In order to increase the efficiency of printing operation, the aforesaid printing pattern films sorted according to the kinds of films are mounted on a pallet and a number of pallets with printing pattern film positioning means are contained in a vertically installed pallet stocker apparatus. Then a desired pallet in the pallet stocker apparatus is moved by mechanical means up to desired height. A printed pattern film carrier, which is reciprocally movable and equipped with a plurality of suction cups, is used to take out each printing pattern film from a pallet and to return the film to a predetermined pallet.
The pallet stocker apparatus for use in a multiplex printer is equipped with a frame formed by removing the front and rear walls from a case. Pairs of guide rails for mounting pallets are installed inside the left and right walls of the frame. A number of pallets (generally made of aluminum about 90 cm (W).times.100 cm (D).times.3 cm (T)) are furnished with printing pattern film positioning means. A group of small wheels arranged on the guide rails support the pallets so that the fairly heavy pallets may travel smoothly and longitudinally along the guide rails. Pallet stoppers prevent the pallets from falling off it they excessively protrude from the case in the longitudinal direction. Means for elevating the frame act to position the pallet loaded with the desired printing pattern films corresponding to the step of printing operation slightly lower than the top height of the printer. Vertically pallet driving means push forward the pallet positioned to the desired height so that the desired printing pattern film may be taken in and out. There are finally provided means for elevating the frame and longitudinally pallet driving means.
However, the conventional pallet stocker apparatus has posed the following problems.
First, since the pallet is drawn toward this side of the frame formed by removing the front and rear walls from the case to take the printing pattern films in and out, the pallet stocker apparatus requires a space in depth equivalent to the length of the pallet in addition to the depth of the case when it is installed.
Secondly, if used for hours, the group of small wheels for the guide rails used to mount the pallets and that of wheel shafts tend to be subjected to frictional damage and besides they are hardly repairable.